FAQs On LOOK Disk Scheduling Algorithm

Q.1: Is Look Disk Scheduling Algorithms Suitable for Solid State Drives (SSD)?

Answer:

Most probably, the Look Disk Scheduling Algorithm is suitable for traditional hard drives. Since SSDs don’t have a moving part, therefore Look Disk Scheduling Algorithm is not so suitable for Solid State Drives.

Q.2: Is Look Disk Scheduling Algorithms fair to all Requests?

Answer:

Look Disk Scheduling Algorithms are not fair to all requests. It mostly prefers to those requests that come in its path, where it is currently scanning.



LOOK Disk Scheduling Algorithm

The LOOK Disk Scheduling Algorithm is the advanced version of the SCAN (elevator) disk scheduling algorithm which gives slightly better seek time than any other algorithm in the hierarchy (FCFS->SRTF->SCAN->C-SCAN->LOOK). It is used to reduce the amount of time it takes to access data on a hard disk drive by minimizing the seek time between read/write operations. The LOOK algorithm operates by scanning the disk in a specific direction, but instead of going all the way to the end of the disk before reversing direction like the SCAN algorithm, it reverses direction as soon as it reaches the last request in the current direction.

The LOOK algorithm services request similarly to the SCAN Algorithm meanwhile it also “looks” ahead as if there are more tracks that are needed to be serviced in the same direction. The main reason behind the better performance of the LOOK algorithm in comparison to SCAN is that in this algorithm the head is not allowed to move till the end of the disk.

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Steps Involved in the LOOK Algorithm

Determine the initial direction of disk head movement. Sort the pending disk requests in the order in which they will be serviced. Scan the disk in the chosen direction, servicing requests as they are encountered. When the last request in the current direction has been serviced, reverse the direction and continue scanning until all requests have been serviced....

Advantages of the LOOK Disk Scheduling Algorithm

It can provide better performance than the FCFS (first-come, first-served) and SSTF (shortest-seek-time-first) algorithms because it reduces the number of head movements required to access data on the disk. It is relatively simple to implement and does not require a large amount of memory or processing power. It is efficient in terms of disk usage because it scans only the areas of the disk where data is located....

Disadvantages of the LOOK Disk Scheduling Algorithm

It may not be optimal in situations where there are large amounts of data to be read or written in one direction, as it could lead to a large number of requests being queued up in the opposite direction. It may not be suitable for real-time systems where fast response times are critical, as it does not prioritize requests based on their urgency or importance. It may lead to starvation of requests that are located far away from the current position of the disk head. Given an array of disk track numbers and initial head position, our task is to find the total number of seek operations to access all the requested tracks if the LOOK disk scheduling algorithm is used. Also, write a program to find the seek sequence using the LOOK disk scheduling algorithm....

Algorithm for LOOK Disk Scheduling

Step 1: Let the Request array represents an array storing indexes of tracks that have been requested in ascending order of their time of arrival. ‘head’ is the position of the disk head....

Example

Input: Request sequence = {176, 79, 34, 60, 92, 11, 41, 114}Initial head position = 50Direction = right (We are moving from left to right)Output:Initial position of head: 50Total number of seek operations = 291Seek Sequence: 60, 79, 92, 114, 176, 41, 34, 11...

Implementation of LOOK Disk Scheduling Algorithm

Implementation of the LOOK Algorithm is given below....

FAQs On LOOK Disk Scheduling Algorithm

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